A prisoner was awoken by an earthquake that caused his wall clock to fall to the floor and rolled in the corner of his cell. When the ground stops shaking, he learns that the clock is still working properly. He can hear it ticking but all he can see now are the hands of the clock. The numbers and markings are printed on the glass cover which was broken from the fall. (see above)
A minute later a jail guard passed by, so the prisoner ask him what time is it. But the jail guard notice the dilemma and just told the prisoner that he will return in an hour and shall give him a key to unlock his shackle (that prevents him to reach the clock) if the prisoner figured out by that time when the earthquake stopped. Another minute passed by, the inspecting warden also notice the prisoner's dilemma when he ask the warden what time is it. The warden just told the prisoner that he will return in an hour and shall unlock his cell door if the the prisoner figured out by then what time he has returned. All the time devices inside the prison are precise and synchronized and alarms at 6 p.m. for bedtime and 6 a.m. for breakfast. How can the prisoner be sure to tell the right (hh:mm) time?